1. Field of the Invention
The present invention relates to an apparatus and method for supplying a power source, and particularly, to an apparatus and method for supplying a DC power source for driving a compressor of an air conditioner.
2. Background of the Invention
Air conditioners are currently using a three-phase motor as a driving motor of a compressor. A power source supply apparatus of the three-phase motor converts Alternating Current (AC) of a commercial power source into Direct Current (DC), and thereafter re-converts the converted DC into the AC using an inverter. The re-converted AC is then applied to the three-phase motor to drive it.
An apparatus for supplying a DC power source according to the related art will now be explained with reference to FIGS. 1 and 2 hereafter.
FIG. 1 is a view showing an apparatus for supplying a DC power source according to the related art.
As shown in FIG. 1, an apparatus for supplying a DC power source according to the related art includes a converter 110 provided with an active filter 111 and a smooth capacitor C to thus convert an AC voltage inputted from a commercial power source into a DC voltage, and an active filter controlling unit 120 for controlling the active filter 111.
The converter 110 outputs the converted DC voltage to an inverter 130. The inverter 130 converts the DC voltage from the converter 110 into an AC voltage to supply it to a three-phase motor 140 for driving a compressor.
The active filter controller 120 includes a synchronous signal generator 121 for generating a synchronous signal by detecting a zero voltage of the DC voltage inputted from the commercial power source, and an on/off controller 122 for generating control signals, which are used to drive power semiconductor devices Q1 and Q2 of the active filter 111, by being synchronized with the synchronous signal generated from the synchronous signal generator 121.
The active filter 111 is composed of a reactor L and the power semiconductor devices Q1 and Q2, and accordingly forms a waveform phase of an input current to be approximately similar to a phase of an input voltage (i.e., to be a sine wave). Hence, the active filter 111 controls the input current to allow a performing of a harmonic removal and a Power Factor Compensation (PFC).
The smooth capacitor C smoothes out an output voltage of the active filter 111 into a DC voltage, and supplies the smoothed DC voltage to the inverter 130.
FIGS. 2(a) and 2(b) are waveform views of an input current of an apparatus for supplying the DC power source according to the related art.
As shown in FIG. 2(a), in an apparatus for supplying the DC power source according to the related art, the power semiconductor devices Q1 and Q2 are alternatively driven once for a certain time within a half period, and accordingly the input voltage waveform toward the smooth capacitor C based upon the AC voltage of the commercial power source has a great peak value of a current with a narrow conducting width.
As shown in FIG. 2(b), for using a small reactor in the apparatus for supplying the DC power source according to the related art, since an input current amount according to load changes is not sufficient, the waveform of the input current is more greatly fluctuated as compared to the waveform of FIG. 2(a) according to the related art in which the small reactor is not used.
However, the apparatus for supplying the DC power source according to the related art drove the active filter 300 without considering the load changes, in case of a high load, it was difficult to satisfy the PFC specification.
Furthermore, in case of a low load, the apparatus for supplying the DC power source according to the related art occurred a loss of the power semiconductor device due to the PFC operation.
In addition, the apparatus for supplying the DC power source according to the related art increased a fabricating cost due to using the reactor L with a great capacity for the harmonic removal and the PFC.